Parallel Interference Cancellation Receiver Research Articles

GPU Accelerated PIC and SIC for OFDM-NOMA

Non-orthogonal multiple access (NOMA) is a candidate multiple access scheme for the fifth-generation (5G) cellular networks. In NOMA systems, all users operate at the same frequency and time, which poses a challenge in the decoding process at the receiver side. In this work, the two most popular receiver structures, successive interference cancellation (SIC) and parallel interference cancellation (PIC) receivers, for NOMA reverse channel are implemented on a graphics processing unit (GPU) and compared. Orthogonal frequency division multiplexing (OFDM) is considered. The high computational complexity of interference cancellation receivers undermines the potential deployment of NOMA systems. GPU acceleration, however, challenges this weakness, and our numerical results show speedups of about from 75–220-times as compared to a multi-thread implementation on a central processing unit (CPU). SIC and PIC multi-thread execution time on different platforms reveals the potential of GPU in wireless communications. Furthermore, the successful decoding rates of the SIC and PIC are evaluated and compared in terms of bit error rate.

Achieving the capacity of half-duplex degraded relay channels using polar coding

In this paper, a novel transmission protocol based on polar coding is proposed for the half-duplex degraded relay channel. In the proposed protocol, referred to as the partial message relaying, the relay only needs to forward a part of the decoded source message that the destination needs according to the exquisite nested structure of polar codes. Theoretically, it is proved that the scheme can achieve the capacity of the half-duplex relay channel under the decode-and-forward (DF) cooperation strategy while enjoying low encoding/decoding complexity. Practically, in order to minimize the global transmission power, the optimization of the power allocation is performed between the source and the relay by using information theoretic tools. Furthermore, a joint iterative soft parallel interference cancellation receiver structure is developed to suit to the proposed scheme. Simulation results show that the proposed scheme outperforms the conventional scheme designed by low-density parity-check (LDPC) codes.

Low Complexity Selective Adaptive Multicarrier DS-CDMA Receiver

In this paper, selective adaptive (SA) receiver for Multicarrier Direct Sequence Code Division Multiple Access (MC DS-CDMA) system is presented. This receiver has high performance and at the same time reduces the multiple access interference (MAI) of the MC DS-CDMA) system with low computational complexity. The performance of SA receiver is measured in terms of the bit error rate (BER). An upper bound expression of the BER for the SA receiver under Rayleigh fading channel condition is derived and validated by computer simulations. Moreover, the implementation complexities of the SA receiver is compared with the Adaptive Parallel Interference Cancellation (APIC) receiver.

DWDM/OOC and large spectrum sources performance in broadband access network

This work presents a performance evaluation based on elaborated analytical expressions of error probability for broadband access network in the case of a combined technique of dense wavelength division multiplexing (DWDM) and one dimensional optical orthogonal codes (1D-OOC). Optical sources with relatively large spectrum has been considered and simulated. Besides the Multiple Access Interference (MAI) at the receiver due to the access method which is optical code division multiple access (OCDMA), the emitted radiation of these sources in a dense WDM communication link introduces additional interference. Conventional correlation receiver (CCR) and parallel interference cancellation (PIC) receiver limitations are discussed. This paper has investigated the kind of optical sources with large spectrum bandwidth which could be accepted for a targeted bit error rate (BER) and given number of users in broadband access network supporting DWDM with optical orthogonal codes.

The Behaviour of Vertical Bell Laboratories Layered Space-Time Algorithm Combined with Multiuser Detection Schemes in Wireless Communication System

This paper provides the performance analysis of multiuser Vertical Bell Laboratories Layered Space-Time (V-BLAST) system receiver structures for Multiple-input Multiple-Output (MIMO) channel at a base station with assumption of perfect channel estimation and perfect timing delay estimation. In MIMO channels the receivers such as decorrelator, Minimum Mean Square Error (MMSE) and Multistage Parallel Interference Cancellation (MPIC) receiver outperform the conventional receiver. Withal, since the multiple antenna interference led to a strong impact on the performance degradation of a multistage interference cancellation receiver, the performance of MPIC receiver was highly degraded based on system loading.

VLSI Implementation of an Adaptive Multiuser Detector for Multirate WCDMA Systems

A multirate receiver for WCDMA systems based on the adaptive signature method was designed and implemented. We employed an adaptive signature algorithm to consider two well-known multirate schemes, namely, the low rate and the high rate detector for variable spreading factor systems. In monorate scenarios, numerical experimentations showed that the adaptive signature method outperforms the Rake receiver and reaches the performances of the soft 4-stage multistage parallel interference cancellation receiver. In multirate scenarios, the performance comparison of two multirate schemes in floating-point and fixed-point was analyzed. Reusing the existing hardware architecture previously developed for monorate systems, we targeted the hardware implementation of these two multirate schemes on FPGA components.

Approach to Interference Cancellation in DS-CDMA Optical Networks

Optical code mutiple access (OCDMA) networks are subject to several limitations, such as multiple access interference (MAI), as well as the noise of the optical components. In this work we propose an interference cancellation technique using the bias mitigation and linear estimators in parallel interference cancellation (PIC) receivers. In order to make the analysis more tractable, the proposed technique is described for a synchronous multiuser communication scenario with multiple access interference in an additive white Gaussian noise (AWGN) channel. Estimates for the error probabilities of the proposed OCDMA detector are derived using the Gaussian approximation for interference terms. Some analytical and numerical results for our system are given and compared with those for other receivers with the same order of complexity.

Robust blind PIC with adaptive despreader and improved interference estimator

AbstractAn effective design of multistage parallel interference cancellation (PIC) receiver using blind adaptive (BA) despreader and pre‐respreader interference estimator for uplink CDMA is proposed and analysed. A novel algorithm is designed, which exploits constant modulus (CM) property of the users' transmitted signals and inherent channel condition to perform adaptive despreading based on minimum error variance criteria. This is carried out by BA weighting of each chip signal for accurate tracking of the desired user's signal power and hence for more improved data detection at the output of each stage of PIC. Furthermore, the despreader weights are used within the adaptive pre‐respreader interference estimation and cancellation to obtain online scaling factors during every symbol period, without any knowledge of users' channels or the use of training sequences. It is found that this way of estimation is optimal in minimum mean squared error sense, and hence, significant reduction in interference and noise variance is observed in detection and estimation of the desired users' signals compared with conventional PIC. Bit error probability of the proposed PIC is obtained using Gaussian Approximation method. Extensive simulation results are shown, which demonstrate impressive performance advantage in fading environments, high system loading, and severe near far conditions. Copyright © 2008 John Wiley & Sons, Ltd.

PIC receiver implementations for the asynchronous UMTS scenarios

In this paper, three different implementations of a multistage partial parallel interference cancellation (PIC) receiver for the asynchronous UMTS signal are presented and compared. The proposed structures take into account the scrambling and channelization codes employed in UMTS and two of them are advanced structures specifically designed to attempt to remove completely the multiuser interference thanks to the addition of specific data buffers for this scenario. The advanced structures proposed outperform the direct implementation of the PIC receiver derived from synchronous CDMA scenarios by taking into account the whole set of interference terms. Also, no windowing is necessary at the receiver and no framing transmission is required.

Multiuser detection with neural network and PIC in CDMA systems for AWGN and Rayleigh fading asynchronous channels

In this paper, multiuser detection in code division multiple access (CDMA) was performed by using neural network (NN) and parallel interference cancellation (PIC). Neural network is used as a front-end stage of one stage PIC circuit. PIC is a classical technique in multi user detection process and its bit error rate (BER) performance is not good in one stage for most of the applications. For improving its BER performance, generally multi stage PIC which has high computational complexity is used. In this study, we have got better BER performance than the three stage PIC receiver in AWGN channel, almost same BER performance with the three stages PIC receiver in the Rayleigh fading channel.

Prime Code Efficiency in DS-OCDMA Systems using Parallel Interference Cancellation

In this paper, we are studying the Prime Codes (PC) efficiency, in direct Sequence Optical Code Division Multiple Access system (DS-OCDMA) using Parallel Interference Cancellation receiver (PIC). We develop the analytical expression of the error probability upper bound in the chip synchronous case, for PC. The main result of our work is that the PIC receiver totally suppresses the effect of Multiple Access Interference (MAI) for Prime Codes, and leads to an error free O-CDMA link in the noiseless case, for whichever employed PC. Simulation results are presented to validate the theoretical analysis. We also show that the PIC receiver permits reducing the required code length for a given Bit Error Rate compared to the Conventional Correlation Receiver. Finally, we compare the PC to the Optical Orthogonal Codes (OOC), and show that the use of PC allows a significant reduction of the required SNR.

2‐Dimensional code design for an optical CDMA system with a parallel interference cancellation receiver

AbstractThe objective of this paper is to design a two‐Dimensional Optical Code Division Multiple Access system (2D‐OCDMA) for application in access networks, with coding and decoding functions performed by electronic devices. We present a new construction method of Multi‐Wavelength Optical Orthogonal Codes (MWOOC), which permits a high flexibility in the code parameters choice. This work evaluates in the noiseless case, the MWOOC potentialities for two receiver structures: a Conventional Correlation Receiver (CCR) and a Parallel Interference Cancellation receiver (PIC). We show that with a PIC receiver, it is possible to design two‐Dimensional codes that respect the access specifications. Copyright © 2007 John Wiley & Sons, Ltd.

Multi-user interference cancellation technology in the presence of multiple frequency offsets

The performance of multi-user detectors in the presence of multiple frequency offsets under a Rayleigh fading channel environment is analysed, and techniques to estimate and remove multiple frequency offsets (FOs) for successive interference cancellation (SIC) and parallel interference cancellation (PIC) receivers are also proposed. The closed form expressions derived for bit error rate (BER) of SIC and PIC schemes in the presence of multiple FOs have been verified using extensive simulation results. The PIC is shown to be less sensitive to frequency offsets as compared to SIC. It is demonstrated through analytical and simulation results that the proposed frequency offset estimation and correction techniques provide approximately 8 dB gain in the BER performance over conventional SIC and PIC schemes in the presence of multiple frequency offsets.

Iterative detection and frequency synchronization for OFDMA uplink transmissions

The problem of frequency synchronization, channel estimation, and data detection for all active users in the uplink of an OFDMA system is investigated in this work. Since the exact maximum likelihood (ML) solution to this problem turns out to be too complex for practical purposes, we derive an alternative scheme that operates in an iterative fashion. At each step, the superimposed signals arriving at the base station (BS) are separated by means of the space-alternating generalized expectation-maximization (SAGE) algorithm. Each separated signal is then passed to an expectation-conditional maximization (ECM)-based processor that updates frequency estimates and performs channel estimation and data detection for each user. The resulting architecture is reminiscent of the parallel interference cancellation (PIC) receiver, where interference is generated and removed from the received signal to improve the system performance. Simulations indicate that the proposed scheme outperforms other benchmark solutions at the price of increased computational complexity

2-Dimensional optical CDMA system performance with parallel interference cancellation

In this paper, we investigate the feasibility of a 2-Dimensional Optical Code Division Multiple Access (2D-OCDMA) system, with electronic coding and decoding functions. We develop a modified construction method of Multi-Wavelength Optical Orthogonal Codes (MWOOC) that permits high flexibility in the code parameters choice. The 2D code performance is calculated for a Conventional Correlation Receiver (CCR) and a more complex one, named Parallel Interference Cancellation (PIC) receiver. For example, for a Bit Error Rate (BER) ⩽10 −9, and 30 simultaneous users, we show that contrary to the CCR, the use of a PIC receiver leads to workable 2D electric coding solutions.

Another Approach for Partial Parallel Interference Cancellation

In this paper, a technique for improving parallel interference cancellation (PIC) receivers with linear estimators is studied in a CDMA system under power control and near-far case. By multiplying the received signal for each user in early stages by a factor superior than unity, the proposed technique significantly reduces the harmful impact of the bias upon BER performance and requires only vector implementation under power control. In order to make the analysis more tractable, the proposed bias mitigation technique is described for a synchronous multi-user communication scenario with binary signalling, non-orthogonal multiple access interference in an additive white Gaussian noise channel.

Channel Acquisition and Tracking for MC-CDMA Uplink Transmissions

This paper deals with channel acquisition and tracking in the uplink of a multicarrier code division multiple access (MC-CDMA) system. The transmission medium is characterized by multipath propagation, and the goal is to estimate the channel frequency response and the noise-power of each active user. Channel acquisition is performed jointly with the noise-power estimation following two different approaches. The first assumes independently faded subcarriers, while the second exploits the fading correlation across the signal bandwidth to improve the system performance. Both schemes are based on the maximum likelihood (ML) criterion and exploit some training blocks carrying known symbols. Channel tracking is pursued through least mean square (LMS) techniques using data decisions provided by a partial parallel interference cancellation (PPIC) receiver. Numerical results are given to highlight the effectiveness of the proposed methods and to present comparisons with other existing solutions

Multiuser detection techniques with decision statistics combining for layered space‐time coded CDMA systems

AbstractThis paper considers a low‐complexity iterative multiuser detection/decoding algorithm in single user layered space‐time coded (LST) systems and LST coded code division multiple access (CDMA) systems. We concentrate on the iterative multiuser receiver based on parallel interference cancellation (PIC) and compare it to the iterative PIC with the minimum means square error (MMSE) detection, as these two approaches seem to be most efficient in meeting the performance‐complexity trade‐off required by practical systems. In iterative PIC structures, a decision statistics bias severely limits the system performance for a large number of multiple access (MA) or multiple‐input multiple‐output (MIMO) interferers. A decision statistics combining (DSC) method, originally proposed for iterative PIC receivers in CDMA systems, is used to minimize the bias effect in space‐time coded systems for iterative PIC receivers. Significant performance improvements have been confirmed with the iterative PIC receiver with DSC (PIC‐DSC) relative to the standard iterative PIC receivers in LST systems for both flat and frequency selective fading channels. This advantage is retained in layered coded CDMA systems as well. The proposed iterative PIC‐DSC detector approaches the performance of the much more complex iterative PIC‐MMSE receiver. Copyright © 2006 AEIT.

Analytical Performance Analysis of the Linear Multistage Partial PIC Receiver for DS-CDMA Systems

In this letter, we derive a recursive expression for the decision statistic of a linear multistage partial parallel interference cancellation (PIC) receiver for direct-sequence code-division multiple-access systems that allow us to present two closed-form expressions (exact and approximate) for the bit-error probability of this receiver. The bit-error rate is computed in terms of the number of PIC stages, set of cancellation parameters, crosscorrelation between the users' codes, amplitude of the users' signals, and noise power.

WCDMA Uplink Parallel Interference Cancellation—System Simulations and Prototype Field Trials

Interference cancellation (IC) is one identified key technology to enhance WCDMA uplink performance. The goal of this contribution is to highlight the relative uplink system capacity improvement available for WCDMA, especially in realistic typical urban radio environments when employing receiver implementations including realistic channel estimation, searcher, and so forth. The performance of the selected limited-complexity parallel IC receiver is first evaluated with link-level simulations in order to provide input to system-level simulations. The system-level methodology is explained and a 40% system-level uplink capacity increase compared to utilizing the conventional RAKE receiver is found. The limited-complexity parallel IC receiver is then evaluated in a single-cell field trial. The trials show that both the mean and the variance of the outer-loop power control is reduced, which implies an overall increased capacity and an increased battery life of the terminals. Furthermore, the observed capacity gains are in accordance with system simulations.